Abstract
This research studies the effect of climate change on the hydrological behavior of two semi-arid basins. For this purpose, the Soil and Water Assessment Tool (SWAT) model was used with the simulation of two future climate change scenarios, one Representative Concentration Pathway moderate (RCP 4.5) and the other extreme (RCP 8.5). Three future periods were considered: close (2019–2040), medium (2041–2070), and distant (2071–2100). In addition, several climatic projections of the EURO-CORDEX model were selected, to which different bias correction methods were applied before incorporation into the SWAT model. The statistical indices for the monthly flow simulations showed a very good fit in the calibration and validation phases in the Upper Mula stream (NS = 0.79–0.87; PBIAS = −4.00–0.70%; RSR = 0.44–0.46) and the ephemeral Algeciras stream (NS = 0.78–0.82; PBIAS = −8.10–−8.20%; RSR = 0.4–0.42). Subsequently, the impact of climate change in both basins was evaluated by comparing future flows with those of the historical period. In the RCP 4.5 and RCP 8.5 scenarios, by the end of the 2071–2100 period, the flows of the Upper Mula stream and the ephemeral Algeciras stream will have decreased by between 46.3% and 52.4% and between 46.6% and 55.8%, respectively.
Highlights
Climate change has become one of the main challenges of the 21st century, with a great effort being made to evaluate and analyze its impact on the hydrological cycle [1,2,3].According to all climatic scenarios, the annual average precipitation will increase in Northern Europe and decrease in the southern Mediterranean regions [4]
Data series are available for the daily average flow (m3 /s) of the entry into the La Cierva and Algeciras reservoirs, corresponding to the periods from 1993–2018 and from 2003–2018, respectively, which allowed the Soil and Water Assessment Tool (SWAT) calibration process to be performed. They are basins with different ephemeral hydrological regimes: the Algeciras stream is an ephemeral stream and the Upper Mula is a transitional watercourse with a dry channel almost all year round except when groundwater provides enough water for stream flow—it is between an ephemeral and a seasonal intermittent stream
Because each climate scenario is subject to the uncertainties inherent to any projection derived from the climate, it is proposed to evaluate the impact taking into consideration a set of climate projections as wide and varied as possible in order to collect a large part of the variability of the climatic hypotheses and reflect the uncertainty (Table 3)
Summary
Climate change has become one of the main challenges of the 21st century, with a great effort being made to evaluate and analyze its impact on the hydrological cycle [1,2,3]. This study is part of the recent line of research based on the application of the SWAT model to assess the impact of climate change on water resources in environmentally fragile basins with high water stress (arid and semi-arid regions). Data series are available for the daily average flow (m3 /s) of the entry into the La Cierva and Algeciras reservoirs, corresponding to the periods from 1993–2018 and from 2003–2018, respectively, which allowed the SWAT calibration process to be performed They are basins with different ephemeral hydrological regimes: the Algeciras stream is an ephemeral stream and the Upper Mula is a transitional watercourse with a dry channel almost all year round except when groundwater provides enough water for stream flow—it is between an ephemeral and a seasonal intermittent stream. Ence periods, 1993–2018 for the Upper Mula basin and 2003–2018 for the Algeciras basin
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